Most commercial properties include a number of building systems that monitor and regulate various functions of the building for the comfort and well-being of the tenants. These building systems include security systems, fire control systems, and elevator systems. One prevalent and important building system is the environmental management system.
An environmental management system is used to regulate the temperature and flow of air throughout a building. The air conditioning for a building typically includes one or more chillers for cooling air and one or more heaters for warming air. Fans distribute air conditioned by a chiller or heater into a duct system that directs the flow of air to the various rooms of a building. Dampers are located within the duct system to variably control an opening to a branch of a duct system or to a room. The dampers are maneuvered through a range of movement from being 100% open to 0% open, i.e., closed, by actuators. Also, the speed of a motor that drives a fan is controlled to regulate fan speed and, correspondingly, air flow in the system. An important component of a building environmental management system is the control system that varies the fan motor speed and the position of the various dampers to maintain pressure and flow rate set points for the system.
In a co-pending patent application entitled “System and Method for Developing and Processing Building System Control Solutions” having Ser. No. 10/668,949 filed on Sep. 23, 2003, which is commonly owned by the assignee of this patent, the disclosure of which is hereby expressly incorporated by reference into this patent in its entirety, a remote system is described for generating environmental management system control programs that are downloaded to buildings for implementation on the building environmental management systems. Development of these control programs requires anticipation of the thermal conditions encountered by the building for which the environmental management system compensates.
The capability of an environmental management system to address thermal conditions depends upon the resources available to the system. For example, chillers are used to take heat from air that is circulated through the ductwork and dampers of the system by the fans. Chillers require chilled water in order to perform their cooling function. Most chillers obtain chilled water by melting ice. The formation and storage of ice for addressing the thermal conditions of a building comprise one function that is managed by the environmental management system for a building. The operator of a building environmental management system prefers to use energy to make ice when the demand for the energy is lower and, therefore, cheaper. Typically, the low demand periods occur at night when operational activities of most businesses and homes are diminished. The operator wants to manufacture enough ice to adequately meet the demands of the following day, but ice that is not used the following day represents a wasted expenditure of energy and money. Therefore, accurate predictions of the thermal load that will be encountered by a building at a particular time period are important for the operation of the environmental management system. These predictions are used to operate and manage the resources of the building prior to that particular time period.
In the example presented above, the ice is melted during the following day to provide chilled water for operating the chillers in the environmental management system. Because the thermal conditions in the building change during the day, the amount of chilled water required to maintain the required environmental conditions for the building also change during the day. Consequently, an accurate profile of the thermal load changes as they are expected to occur would be useful for operating the environmental management system so that the right amount of chilled water is available for compensating the current environmental conditions.
One method for predicting building thermal conditions requires the forecasting of conditions that are exogenous to the building, namely, weather conditions, and the use of these predicted weather conditions in an energy simulation software package. Such energy simulation software is available from the Department of Energy. In order for the software to operate, however, building configuration data must be collected and input in the software. The building configuration data includes geometrical dimensions, orientation of the building, location parameters, and the like. These data are taken one time, but the collection of this data, even on a one time basis, can be labor intensive and costly. Also, additional sensors may be required for the collection of these data and the cost of installing and operating these sensors may be cost prohibitive. Additionally, the computational resources required for the timely generation of predicted thermal loads by this method are significant.
Statistical programs have also been used in an effort to predict building thermal loads. These programs attempt to find a correlation between a predicted load and predicted independent parameters. One problem with statistical programs is the use of a particular function for correlating the inputs to the outputs. For example, a statistical program may use a linear, second degree polynomial, or exponential relationship to correlate inputs to outputs. Determination of the right function is performed using trial and error techniques and the result is applicable only to the particular building for which it was developed. Also, the complexity of fitting a solution for the determined function to multiple variables that behave in a non-linear manner requires the use of complex algorithms for optimizing multiple parameter systems. Furthermore, convergence of solutions is not guaranteed.
What is needed is a system for predicting thermal load conditions for a building to facilitate the development of environmental control solutions.
What is needed is a system for predicting thermal load conditions for a building that is adaptable to multiple buildings.
What is need is a system for predicting thermal load conditions for a building that does not require extensive computational resources for the timely generation of thermal loads.
What is needed is a system that correlates inputs to outputs without requiring a determination of a particular function to which the input/output mapping must conform.
What is needed is a system for predicting thermal load conditions for a building that does not require the installation of additional sensors for a building environmental management system.